Such an electrical stimulation device is for instance used in the fields of functional electro-stimulation (also often indicated as FES) and in the fields of pain suppression via electrical stimulation signal (also often indicated as transcutane electronic nerve stimulation, or in short TENS). In both FES and TENS electrical signals are locally applied to the body of a human or animal so as to excite particular parts of the nervous system. In particular a small electrical current is locally applied to the skin of the human or animal undergoing electro-stimulation. It has been found that such electro-stimulation has various beneficiary effects. As indicated above, pain suppression is one of the beneficial effects known. Furthermore, it has also been found that local electro-stimulation can activate muscular tissue and may activate the healing of wounds. In order to achieve optimum beneficiary effects, the electrical signals are to be applied to particular, optimum positions on the person or animal skin. It is known that some optimum positions on the skin have locally different electrical impedance values, hence optimum stimulation positions may be derived from electrical impedance measurements.
Such an electro-stimulation apparatus is known from the patent application WO 99/52588. The known electro-stimulation apparatus as disclosed in the cited patent application comprises an electrode system which measures local electrical impedance. The electrode system includes a multitude of electrode pads and a counter electrode held at a reference voltage.
A drawback of the known electro-stimulation apparatus is that the correct placement of the electrode for applying electrical stimulation for pain suppression still requires considerable anatomical and physiological knowledge and experience.